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Beneficial Lactic Acid Bacteria
Published in K. Balamurugan, U. Prithika, Pocket Guide to Bacterial Infections, 2019
The other substances produced by LAB are mannitol, sorbitol, tagatose, and xylitol used as sweeteners in food industry. Mannitol is a six-carbon sugar alcohol synthesized by bacteria from fructose using mannitol dehydrogenase (Patra et al. 2009; Papagianni 2012). The research revealed that one-third of fructose could be replaced with glucose, maltose, galactose, mannose, raffinose, or starch with glucoamylase, and two-thirds of fructose could be replaced with sucrose for mannitol production (Saha and Nakamura 2003). Tagatose is an isomer of fructose showing prebiotic effect and antioxidant activity, and it can be used for control of diabetes and obesity. D-tagatose can be produced from D-galactose by L-arabinose isomerase (araA) (Chouayekh et al. 2007; Patra et al. 2009). Sorbitol is another six-carbon sugar alcohol produced by catalytic hydrogenation of glucose, with applications in the food and pharmaceutical industries. Only a few organisms are able to synthesize sorbitol. LAB strains are often subjected to metabolic engineering to achieve sorbitol hyperexpression (Patra et al. 2009; Papagianni 2012). Xylitol is a five-carbon sugar alcohol produced by reduction of xylose. LAB have not been reported to produce xylitol naturally, but recombinant strains with xylose reductase were able to generate this compound (Papagianni 2012). Bacteriocins are considered in the separate chapter.
Role of Fructose 2,6-Bisphosphate in the Control of Glycolysis in Liver, Muscle, and Adipose Tissue
Published in Rivka Beitner, Regulation of Carbohydrate Metabolism, 1985
Incubation of hepatocytes from fed rats with relatively high concentrations (20 mM) of keto-hexoses such as D-fructose, D-tagatose, and L-sorbose caused a drastic decrease in fructose-2,6-bisphosphate.75 In the presence of high concentrations of glyceraldehyde and glycerol, but not dihydroxyacetone, fructose-2,6-bisphosphate was also greatly reduced. Except dihydroxyacetone, all these compounds have the common property of causing a rapid accumulation of ester phosphates and, in so doing, deplete the adenine nucleotides and the Pi pools of the cell.76 Incubations of hepatocytes with 20 mM lactate also caused a fall in fructose-2,6-bisphosphate which became comparable to values obtained after glucagon treatment. Pyruvate and alanine had a less marked effect.75 The mechanism by which lactate, and to a lesser extent alanine and pyruvate, decrease fructose-2,6-bisphosphate is not known. This effect may result from an inhibition of phosphofructokinase-2 by phosphoenolpyruvate, which accumulates in livers perfused with these substrates.50 As a result of the decrease in fructose-2,6-bisphosphate, gluconeogenesis is favored and the glycolytic flux is inhibited at the level of phosphofructokinase.
Exopolysaccharides metabolism and cariogenesis of Streptococcus mutans biofilm regulated by antisense vicK RNA
Published in Journal of Oral Microbiology, 2023
Yuting Sun, Hong Chen, Mengmeng Xu, Liwen He, Hongchen Mao, Shiyao Yang, Xin Qiao, Deqin Yang
Next, we explored the mechanism of ASvicK regulating biofilm and EPS formation. We found that overexpression of ASvicK generated impact on the EPS metabolism-related genes gtfB/C/D, ftf and vicK. Meanwhile, the ability to produce VicK protein and the enzyme activity of GTFs were diminished. Numerous studies have confirmed that VicK plays a crucial role in the biofilm formation of S. mutans and the expression of genes related to EPS metabolism [17,41]. Deletion of vicK results in down-regulation of gtfD, ftf and gbpB [35]. These studies are consistent with the results that down-regulation of the vicK gene in our ASvicK strain carried out decreased expression of gtfB/C/D and ftf. GTFs enzymatic activity was significantly reduced in ASvicK overexpressing strains, again confirming that ASvicK RNA affects EPS synthesis by affecting GTFs. In the previous results of GC-MS, the galactose fraction of ASvicK overexpressing strains increased. Lactose metabolism is mainly hydrolyzed into glucose and galactose-6-phosphate (Gal-6-P) through the tagatose pathway and LeIoir pathway [42,43], which is released from Lac-6-P. Glucose can be phosphorylated by galactokinase (GalK) before entering glycolysis [44,45]. In this study, the lacA/B/C/D/E/G/R genes involved in the lactose metabolism tagatose pathway and galK and galT gene expression was significantly increased. Therefore, lactose and galactose participate in the complex regulatory mechanism of EPS metabolism.
The potential role of gut microbiota and its modulators in the management of propionic and methylmalonic acidemia
Published in Expert Opinion on Orphan Drugs, 2018
Alberto Burlina, Sebastian Tims, Francjan van Spronsen, Wolfgang Sperl, Alessandro P. Burlina, Mirjam Kuhn, Jan Knol, Maryam Rakhshandehroo, Turgay Coşkun, Rani H Singh, Anita MacDonald
D-tagatose, manno-oligosaccharides [63,64], and arabinoxylan oligosaccharides [65] need to be synthesized and added as food additives. However, D-tagatose occurs naturally, but only in small amounts in fruits and dairy products. Polydextrose also needs to be synthesized, and is used widely as a bulking agent in several prepared foods [65]. Ispaghula husk is known only for medicinal use (softening of the stools) and can be easily avoided. Only inulin is naturally present in noticeable amounts in various flowering plants, such as chicory, Jerusalem artichokes, salsify, asparagus, and onions [66–69]. However, food preparations, such as boiling, might reduce the inulin content of these foods as inulin is soluble in hot water.
Mass Spectrometry-based Biomarkers for Knee Osteoarthritis: A Systematic Review
Published in Expert Review of Proteomics, 2021
Mirella J.J. Haartmans, Kaj S. Emanuel, Gabrielle J.M. Tuijthof, Ron M. A. Heeren, Pieter J. Emans, Berta Cillero-Pastor
Interestingly, arachidonic acid, ethanolamine and malate were decreased in the OA group when compared to non-OA patients [37,42], but increased in the late OA group when compared to early OA [43]. In addition, Kim et al. found differences in metabolites between patients with OA KL grade 1, 2, 3 and 4 specifically [43]. Levels of sugar (alcohols) such as arabitol, galactose, glucose, mannose and tagatose were increased in KL grade 1 compared to other stages. Urate, β-alanine, pyruvate, and terephthalate levels were increased in KL grade 2 patients and fatty acids, proline, phenylalanine, squalene, and trehalose-6-phosphate were increased in KL grade 3 and 4 [43].